The present invention relates to a process for processing, treating and utilizing coke oven gas.
It is known that coke ovens, used to form coke, discharge gases which have a relatively high temperature and which contain a great many impurities. For environmental reasons it is not possible to discharge such coke oven gases directly to the atmosphere. It has accordingly been a common practice to cool coke oven gases by subjecting the coke oven gases to a condensation operation. Both the gaseous and liquid components resulting from such a condensation operation are further treated in a secondary recovery installation to remove the impurities therefrom, and particularly to separate tar, ammonia, sulfur, benzene and naphthalene. It is also known to use the thus purified coke oven gas for the under-grate firing of the coke ovens. It is additionally known, when the coke ovens are part of an overall installation of a steel mill or other metallurgical plant which includes at least one shaft furnace, for example a blast furnace, that the waste gas from the blast furnaces may be used for the under-grate firing of the coke ovens.
However, in recent years the market for the products recovered from the secondary recovery treatment of the coke oven gases has fallen. Accordingly, the secondary recovery treatment operation has become uneconomical, and such secondary recovery treatment operation is generally now performed only to purify the coke oven gas. In fact, the products of the secondary recovery treatment operation are conventionally at least partially destroyed, as exemplified by the now common practice of combustion of the ammonia recovered from the secondary recovery treatment operation of the coke oven gas.
Accordingly, the sensible heat of the coke oven gas is to a very large degree wasted in conventional installations. It of course would be of great practical advantage to be able to utilize the sensible heat of the coke oven gas in other heat consuming operations. Coke oven gas generally has a temperature of approximately 700.degree. to 750.degree. C. upon discharge from the coke ovens. If it would be possible to use this heat, then not only would the cost of the secondary recovery treatment operation be saved, but also potential damage to the environment would be reduced, since the coke oven gases would not be discharged to the atmosphere.
In German DT-OS No. 22 32 650, there is disclosed a process for preparing a reducing gas by heating an exhaust gas from the upper side of a reducing furnace, for example a blast furnace, with a methane-containing gas, for example coke oven gas, natural gas, or the like. Specifically, there is introduced into a reforming furnace a mixture of methane or methane-containing hydrocarbon gas, for example a cooled and purified coke oven gas, which was subsequently heated to a temperature below 1000.degree. C., and a gas which contains CO.sub.2, H.sub.2 O, etc., for example the exhaust gas from a blast furnace, and which was heated to a temperature of more than 1250.degree. C. The resultant mixture is reformed into a reducing gas by heating the mixture in the reforming furnace to a temperature higher than 1200.degree. C. There is thus obtained a gas mixture having a relatively high inert fraction, particularly nitrogen.
Additionally, German Patent Application No. P 26 38 348.2, corresponding to U.S. application Ser. No. 827,809, filed Aug. 25, 1977, provides a method for further processing coke oven gas.
All of these and other known methods for processing and utilization of coke oven gas, however, are not entirely ideal.